This document deals with one of the most common errors encountered while using the transaction FAGL_ACTIVATE_OP to enable open item management for a specific account - "Ledger group-specific postings exist" (error message no. FAGL_ SWITCH_OP090)
After executing the report you notice that the conversion has stopped and produced the following error message on the output screen:
What this means is that there are line items in the account being converted have a Ledger Group value (in the corresponding field in BKPF-LDGRP) filled with a value indicating that it is a ledger group specific line item.
The conversion then stops since it is not possible to convert accounts to Open Item Management which have existing line items with Ledger Group.
This error message appears not for a technical restriction, but a logical one; since is not possible at all to set the 'ledger group specific' postings to standard open item management. The reason for this should be clear, as the main requirement/requisite for Open Item management is that the balances in ALL ledgers must be the same as the sum of open items. Therefore it is not possible to post 'ledger group specific postings' anymore for a open item managed account. So of course, ledger group specific postings will not be set to Open Item Management, as these could also not be cleared again.
Please also see the KBA 2058990 for additional details in relation to this.
Additional information on the use of FAGL_ACTIVATE_OP can be found in the wiki here